Implants and infection

With the increasing use of medical implants, we are also increasingly confronted with infectious biofilms on them. The most common implants include joint prostheses, osteosyntheses, vascular prostheses, pacemakers and defibrillators, dental implants, neurosurgical shunts and breast implants.

The therapeutic success of implant infections depends on a precise microbiological diagnosis. Because microorganisms form biofilms on foreign bodies, they are often difficult to detect in surrounding tissue. Biofilms consist of an amorphous matrix of polymerized polysaccharide in which microorganisms are embedded. In the biofilm, microorganisms are in a metabolically inactive, stationary growth phase. Over weeks to years, a complex three-dimensional layer develops which ensures the nutrition of the biofilm (via water channels) and its communication (via extracellular messenger substances) via rudimentary structures.

While free living (planktonic) bacteria are killed by antibiotics and the immune system, adherent bacteria survive protected in the extra cellular matrix of the biofilm.

Technical details can be found in the data sheet.

Significance and principle of action of sonication

Through sonication (ultrasound), microorganisms can be gently removed from the surface of an infected implant. The implant is immersed in liquid so that the ultrasound waves can act on the entire implant surface. After sonication, the liquid (the sonicat) is prepared for cultures and can then immediately be used for subsequent analysis (e.g. PCR). Sonication enables rapid diagnosis of the site of infection if implants have to be removed.

Detection of biofilm-forming bacteria

The implant is aseptically removed from the body in the operating room and transported to the microbiology laboratory in a sterile box within 24 hours. After addition of Ringer’s solution, the implant is shaken vigorously and exposed to ultrasound for 1 minute.

The sonication removes > 99.9% of the adherent bacteria.

Quantitative detection of biofilm-forming bacteria

The sonication is microbiologically processed and the amount of bacteria is quantified (number of colony forming units per ml sonication fluid). Sonication can detect up to 10,000 times more bacteria than conventional methods, such as biopsies of periprosthetic tissue. This allows better detection of mixed infections and different bacterial morphotypes.

The sensitivity is particularly improved in patients with previous antibiotic therapy because the bacteria protected in the biofilm survive better.

operating principle

In order to gently remove the biofilm, the implant, which is deposited in a box with liquid, is placed in the BactoSonic® specially developed for this procedure; a sonication in an ordinary ultrasound bath would kill the microorganisms. Low-frequency ultrasound with low intensity in the area of the cavitation threshold is used. The adhesion of the biofilm to the implant surface is reduced by microcurrents, shear forces and oscillating cavitation bubbles to such an extent that it detaches from the implant during the ultrasonic treatment. Any cavitation events that occur are still so low in energy that no significant destruction of cell structures occurs. The microorganisms obtained in the sonication can be cultivated directly or detected promptly by other methods.

Planktonic and biofilm forms of bacteria

Biofilm on the implant surface

Success of biofilm removal

Comparison of cultures of tissue biopsy and sonication fluid (Sonikat)

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1. Achermann Y, Vogt M, Leunig M, Wust J, Trampuz A. Improved diagnosis of periprosthetic joint infection by multiplex polymerase chain reaction in sonication fluid of removed implants. J Clin Microbiol 2010; 48 (in press).

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3. Bonkat G, Rieken M, Rentsch CA, Wyler S, Feike A, Schäfer J, Gasser T, Trampuz A, Bachmann A, Widmer AF. Improved detection of microbial ureteral stent colonisation by sonication. World J Urol 2010; (in press).

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5. Clauss M, Trampuz A, Borens O, Bohner M, Ilchmann T. Biofilm formation on bone grafts and bone graft substitutes. Comparison of different materials by a standard in vitro test and microcalorimetry. Acta Biomaterialia 2010 (in press).

6. Del Pozo JL, Tran NV, Petty PM, Johnson CH, Walsh MF, Bite U, Clay RP, Mandrekar JN, Piper KE, Steckelberg JM, Patel R. Pilot study of association of bacteria on breast implants with capsular contracture. J Clin Microbiol 2009; 47:

7. Gorisek N, Bombek M, Kramberger S, Tomazic T, Dolinar D, Kocjancic B, Trampuz A. Sonication of removed orthopedic devices significantly improves the diagnosis of infection. 2010 (in revision).

8. Kobayashi N, Bauer TW, Tuohy MJ, Fujishiro T, Procop GW. Brief ultrasonication improves detection of biofilm-formative bacteria around a metal implant. Clin Orthop Relat Res 2007;457: 210-3.

9. Monsen T, Lövgren E, Widerström M, Wallinder L. In vitro effect of ultrasound on bacteria and suggested protocol for sonication and diagnosis of prosthetic infections. J Clin Microbiol. 2009; 47: 2496-501.

10. Piper KE, Jacobson MJ, Cofield RH, Sperling JW, Sanchez-Sotelo J, Osmon DR, Steckelberg JM, Mandrekar JN, Fernandez SM, Patel R. Microbiologic diagnosis of prosthetic shoulder infection using implant sonication. J Clin Microbiol 2009; 47:

11. Rieger UM, Pierer G, Lüscher NG, Trampuz A. Sonication of removed breast implants for improved detection of subclinical infection. Aesth Plast Surg 2009; 33: 404-408.

12. Rohacek M, Weisser M, Kobza R, Schoenenberger A, Pfyffer G, Frei R, Erne P, Trampuz A. Bacterial colonization and infection of electrophysiologic cardiac devices detected with sonication and swab culture. Circulation 2010 (in press).

13. Sendi P, Frei R, Maurer TB, Trampuz A, Zimmerli W, Graber P. Escherichia coli variants in periprosthetic joint infection: diagnostic challenges with sessile bacteria and sonication. J Clin Microbiol 2010; (in press)

14. Trampuz A, Osmon DR, Hanssen AD, Steckelberg JM, Patel R. Molecular and antibiofilm approaches to prosthetic joint infection. Clin Orthop Relat Res 2003; 69-88.

15. Trampuz A, Zimmerli W. Prosthetic joint infections: update in diagnosis and treatment. Swiss Med Wkly 2005; 135:

16. Trampuz A, Piper KE, Hanssen AD, Osmon DR, Cockerill FR, Steckelberg JM, Patel R. Sonication of explanted prosthetic components in bags for diagnosis of prosthetic joint infection is associated with a risk of contamination. J Clin Microbiol 2006; 44: 628-31.

17. Trampuz A., Piper KE, Jacobson MJ, Hanssen AD, Unni KK, Osmon DR, Mandrekar JN, Cockerill FR, Steckelberg JM, Greenleaf JF, Patel R. Sonication of removed hip and knee prostheses for diagnosis of infection. N Engl J Med 2007; 357:

18. Trampuz A, Zimmerli W. Diagnosis and treatment of implant-associated septic arthritis and osteomyelitis. Curr Infect Dis Rep 2008; 10: 394-403.

19. Trampuz A, Steinrücken J, Clauss M, Bizzini A, Furustrand U, Uckay I, Peter R, Bille J, Borens O. New methods for the diagnosis of implant-associated infections [article in French]. Rev Med Suisse 2010 (in press).

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